Glass spheres and underground proppants and methods of making the same



United States Patent 3242 032 GLASS SPHERES AND UNDEnoRoUND PROP- PANTSAND METHODS OF MAKING THE sAME conditions of incipient fusion, thenquenching the particles from a temperature above about 650 C. in a fluidto form glass spheres. I have found that the quenching fluid may be aliquid having a viscosity greater than water,

Charles W. Schott, 4769 Barone Drive, Pittsburgh 27, Pa. 5 but t t aloneCalm be Psedi N0 Drawing FilediNmh 24 1961. Sen 154,381 It is importantthat the moving bed of carbonaceous 6 Claims, (C 1 1 1) material not becombusted during the heating operation since it would result in stickingtogether of the glass This application is a continuation-in-part of mycoparticles. In addition, combustion of the carbonaceous endingapplication Se ial No 804,593, filed April 7, 10 material would preventtheability to recycle the car bo- 1959,. naceous material. For thesereasons, a carbonaceous ma- This invention relates to glass spheres andunder terial having a low chemical reactivity rate (such as groundproppants and methods of making the same and acetylene black isrequired. Furthen it is necessary to particularly to high strengthspheres of glass. operate the apparatus under conditions that permitonly There has long been a demand for high strength spheres a minimum ofair leakage into the heating zone thereby of glass for use as acki gmaterial for chemical reaepermitting no substantial combustion of thecarbonaceous tion towers, as porous load supporting beds, as corrosionmaterial. 7 I resistant rollers and for various other purposes. There Ihave found that the higher the temperature from has in addition been avery realneed for an underground which the glass is quenched the higherthe compressive proppant for use in oil and gas wells and the like topro strength will be. have found that for high strength mavide a path offluid flow in a fractured formation. Variterials it is necessary toquench from a temperature not ous materials have been used with varyingdegrees of l ss than 650 C. I have found that glas ses may be airsuccess. For example, graded sand has been used but quenched totemperatures approaching 650 C. and then it lacks sphericity and has nostrength in larger sizes. finally quenched according to the practices ofmy inven- Walnut shells and aluminum shot have been used but tlOIl andobtain the high SIIE IIgth S characteristic Of my they tend to flattenout. Glass spheres have heretofore inv nt n F r Xampl glass s q n h dfrom 1000 been made in various Ways but the products have always 0 ydropping through air to a temperature of 675 C. lacked the property ofhigh strength. Such spheres in and then into oil at room temperaturewill have a higher the form of solid non-porous spheres have generallyhad strength than identical spheres which are treated by concompressivestrengths less than 10,000 lbs. per square l n l q i g p ac ices Su hpher s Will have inch and accordingly were of limited usefulness. Due tothe high smngths and mslstflnce t0 crushlng Whlch 15 this compressivestrength limitation, such prior spheres necessary gw lmppfm v I v werenever seriously considered for underground prop- Pmctlce of y mventloflW m l' fully undcl" pant uses. In the form of cellular spheres with anim- Stood P f l m h Q l3 P perforate outer shell, such materials andlittle or no Ordm'ary hme'soda'slhFate glass was gushed and strengthgraded to produce a fraction between and 20 mesh. I have discovered anunderground proppant and math This fraction was mixed in the proportionsof 2000 grams 0d of roducin solid bodies of lass havin enerau of glassand 320 grams of acetylene black. This mixture h h g t a g 6 was heatedin a moving bed kiln to a temperature of SP enca S z g i 11 sz g g g O40 1000 C. until the glass particles became spherical. The l Per SquareInc as 1g as 4 1 per Square acetylene black and glass particles weredischarged into and adapted as underground proppzlmsa bath of ethyleneglycol at room temperature have found h solld ph of glass havlng theafter 2 feet of free fall in air. The glass spheres were hlgh Strengthneededfof l PI PP 11563 Can recovered after reaching room temperature.The glass Producfid y heatlngglass Particles In movlflg 40 spheres weretested under compression and found to of carbonaceous mater1al to atemperature in excess have an average compressive strength of about98,000 maintained at about 1000 C. to cause particle surface lbs. persquare inch. These tests were made by placing Table Depth ConcentrationFracture Equivalent, Size U.S. Flow Formation Over burden Type SeriesMesh Capacity Remarks Pressure Particles per Lb./ Gal in (ind-ft.)

(p.s.i.) sq. in. Fracture Sand 10-20 6.0 17,000 Moderately embedded,Slightly crushed. d0 8-12 64 6.0 8,000 Moderately embedded, moderatelycrushed. Rounded wal- 6-8 10 0.8 20,000 Slightly embedded, Slightly nutshells. pancaked. Aux Vases Sand... 3,000 Glass spheres... 6-8 31 5.9118,000 Moderately embedded, ver

slightly crushed. Sand 4-6 15 6.0 10,000 Moderately embedded, Veryseverely crushed. Rounded wal- 4'6 5 0.8 25,000 Moderately embedded,Slightly nut shells. pancaked. Ottawa Sandm. 1020 Monolayer pack. 700Slightlfiv Embedded, Severely Dowell Sand... 842 do 100 50. Rounded Wal-8-12 20. 0.8 13,000 Slightly embedded, Mod- Connell Sand 6, 000 nutshells. erately pancaked.

Alurfiinum 8-12 20. 48,000 Do.

pe eivs. Glass spheres 842 44 a. 4.0 116,500 Slightly embedded, Veryslightly crushed.

the spheres between two hardened steel plates (Rockwell C hardness of25) and exerting a force on the plates so that there was essentiallypoint contact on the spheres.

These spheres were divided into three groups having size and strengthproperties as follows:

Average compressive Mesh size: strength, p.s.i. 6 to 8 105,207

The spheres were then placed in laboratory flolw cells constructed fromtypical well strata and compared with conventional proppants in the samestrata. The results of fracture flow capacity tests and othercomparative physical data are set out in the preceding table.

The foregoing table shows that the proppant of this invention permits afracture flow capacity far greater than any of the conventionalproppants. This material in addition to providing this greater fractureflow capacity, has other highly desirable characteristics. The materialis of uniform graded size and spherical shape. It is resistant tochemical attack by the ordinary corrosion agent to be found in soils andunderground structures. Finally, it is of more uniform compressionstrength and density and does not deteriorate with the formation ofundesirable chemical by-products.

The fracture flow capacity is recorded in millidracy feet of flow(-md.-ft.). This is a well recognized method in the oil industry ofdetermining the effectiveness of propping agents. It is determined bymultiplying the permeability in darcys by the width of the fracture inwhich the propping agent is placed. High fracture flow capacities meanlarger recoveries from the fracture area and is of utmost significanceto petroleum and gas recovery.

I have found that I may use as the starting material for the preparationof high strength proppants any of the higher melting heat resistingglasses as well as ordinary soft glasses.

I have found that the glass may be spheroidized by the practicedescribed in the example or by the methods described in my copendingapplication Serial No. 775,547 filed November 21, 1958, now PatentNumber 3,148,045, or by any other method of spheroidizing such :as bystriking a molten bath with a rotating disc, passing the molten glassthrough a screen, blowing from -a bath, aspirating from a stream orpool, which will permit the glass to be discharged as a sphere at thehigh temperature here contemplated into a quenching media heredisclosed.

I have found that water alone cannot be used as the quench at anytemperature within the practice of my invention. Apparently, the hightemperatures from which quenching must be carried out in order toachieve my results cause excessive strains when the material is quenchedin water or for some reason the water fails to properly remove the heat.In any event, all attempts to quench in water have resulted in failure.On the other hand, aqueous solution of water glass, aqueous solution ofstarch such as cornstarch, aqueous solutions of soap and aqueoussolutions or dispersions of certain water soluble organic materials suchas ethylene glycol have produced satisfactory quenching.

I have found that such glass proppants as are here described must have adensity below about 2.6 gm./ cc. in order that they may be properlysuspended in conventional fracturing fluids which carry the proppantinto the strata which is to be supported, These glass proppants arechemically inert at 250 F. This is necessary in order to prevent theirbeing chemical-1y attacked and eroded by brine and other sub-surfacecorrosive agents. The pH range encountered in sub-surface strata mayvary from about .pH 3 to pH 11 and the proppant must be able towithstand such varying conditions. This means that the proppant must bechemically stable in both acid and alkaline environments. Since thebottom hole temperatures of oil and gas wells may be considerably higherthan the surface temperatures the proppant must be physically stable attemperature of up to 250 F. in order to satisfactorily serve as aproppant. In addition, the proppant to be pumpable must have smoothsurfaces of generally spherical shape as well as high strength.

In the foregoing specification, I have set out certain preferredpractices and embodiments of my invention. However, it will be evidentthat the invention may otherwise embodied within the scope of thefollowing claims.

I claim:

1. A method of making high strength bodies of glass having a generallyspherical shape, comprising the steps of heating said glass body to atemperature above its softening point and introducing said heated bodyat a temperature above its softening point into a quenching fluid.

2. A method of making high strength bodies of glass having a generallyspherical shape, comprising the steps of heating particles of glass in amoving bed of carbonaceous material of low chemical reactivity,maintaining the moving bed at a temperature above the softening point ofthe glass under atmospheric conditions that permit no susbtantialcombustion of the carbonaceous material to cause particle surfaceconditions of incipient fusion and introducing said heated particles ata temperature above their softening point in a fluid into a fluid quenchat ordinary room temperatures which fluid has a viscosity greater thanwater.

3. A method as claimed in claim 1 wherein the quenching fluid is anoleaginous fluid.

4. A method as claimed in claim 1 wherein the quenching fluid isethylene glycol.

5. A method as claimed in claim 1 wherein the quenching fluid is anaqueous starch solution.

6. An article made according to the method of claim 1 which ischaracterized by a compressive strength in excess of 50,000 lbs./in. andby resistance to chemical attack at temperatures of about 250 F.

References Cited by the Examiner UNITED STATES PATENTS 1,596,105 8/1926Kelly 161-1 2,460,977 2/ 1949 Davis et al. 21 2,919,471 1/1960 Hechinger18-47.2 2,950,247 8/1960 McGuire et al. 2528.55 2,963,824 12/1960Pinotti 6521 3,075,581 1/1963 Kern 16642 3,081,209 3/1963 Chan et al.1611 3,149,016 9/1964 Tung 1611 FOREIGN PATENTS 4,372 12/1874 GreatBritain.

OTHER REFERENCES Handbook of Glass Manufacture, vol. I, ed. by F. V.Tooley, 1953, Odgen Pub. Co., New York, pp. 23-25 relied on.

DONALL H. SYLVESTER, Primary Examiner.

JOSEPH REBOLD, Examiner,

1. A METHOD OF MAKING HIGH STRENGTH BODIES OF GLASS HAVING A GENERALLYSPHERICAL SHAPE, COMPRISING THE STEPS OF HEATING SAID GLASS BODY TO ATEMPERATURE ABOVE ITS SOFTENING POINT AND INTRODUCING SAID HEATED BODYAT A TEMPERATURE ABOVE ITS SOFTENING POINT INTO A QUENCHING FLUID.
 6. ANARTICLE MADE ACCORDING TO THE METHOD OF CLAIM 1 WHICH IS CHARACTERIZEDBY A COMPRESSIVE STRENGTH IN EXCESS OF 50,000LBS./IN.2 AND BY RESISTANCETO CHEMICAL ATTACK AT TEMPERATURES OF ABOUT 250*F.